Sodium-sulfur batteries are known in the art and are described for example in U.S. Pat. Nos. 3,476,602 and 3,679,480. A solid glass electrolyte is described for example in U.S. Pat. No. 3,829,331. The general state of the art is described in the article "The Dow Sodium Sulfur Battery", which appeared in the Journal: Proceedings of the 7th IECEC, 1972, pages 50-53, published by the American Chemical Society, 1972.
According to the aforementioned article, a battery of the capacity of 40 Ampere-hours contains 27,000 glass fibers of a length of 11.5 cm. The fibers are filled with sodium and communicate with a sodium reservoir via a perforated plate. The perforated plate constitutes a wall of the reaction chamber which contains the positive mass and the glass capillary tubes. The very large number of fibers is necessitated by the high specific resistivity of the glass (quoted in the above article to be 5.times.10.sup.5 ohm-cm) coupled with the requirement for a relatively low internal battery resistance. The large number of fibers creates a large surface area of the electrolyte and makes possible a relatively low operational current density of only a few mA/cm.sup.2.
It is apparent that the disposition and filling of such a very large number of glass capillaries is technically difficult and economically expensive. A critical factor in the construction of such a cell is the tendency of the glass to fracture in the transition zone from the hollow fiber having a wall thickness of approximately 10.sup.-2 mm to the perforated plate which is of approximately a thickness of 5 mm. Another factor contributing to a difficult construction is the tendency of the capillary wall to be deformed in the transition region.
A further problem arises from the corrosiveness of the positive electrode mass. According to U.S. Pat. No. 3,749,603, current is conducted away from the capillaries by an aluminum foil coated with MoS.sub.2. This protective coating must be perfectly continuous and pore-free and thus requires a relatively high effort to obtain, especially because each capillary must be associated with a particular section of foil at a predetermined distance.
It does appear clear that it would be a substantial advantage if the specific resistivity of the glass electrolyte could be reduced because a corresponding reduction of the number of capillary tubes would then be possible for a given capacity. Furthermore, for a given total weight of glass electrolyte the diameter of each capillary tube could be substantially enlarged which would facilitate the construction and reduce the cost.